<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>盒子模型单方向边框线</title>
</head>
<style>
    .box1{
        width: 200px;
        height: 200px;
        background-color: pink;
        border-top: 10px solid red;
        border-right: 10px solid green;
        border-bottom: 10px solid blue;
        border-left: 10px solid yellow;
    }
</style>
<body>
    <div class="box1"> div标签 </div>
</body>
</html>